1. Field of the Invention
The present invention relates to fiber optic cable systems and, more specifically, to a fiber optic drop for providing continuous, uninterrupted fiber optic service from a service provider central office to a subscriber premises.
2. Definitions
The following definitions and descriptions are provided to clearly define the intended meanings of certain terms used throughout this application.
1. Primary fiber optic strandxe2x80x94a fiber optic strand that is connected to an electronic device in the central office of a service provider. A primary fiber optic strand supports a single fiber optic electronic device in the central office and up to 32 different fiber optic electronic devices external to the central office, i.e., one fiber optic strand can be split into 32 different strands for connection to 32 different fiber optic electronic devices.
2. Fiber optic cablexe2x80x94a cable that contains a multiple number of fiber optic strands.
3. Distribution splitterxe2x80x94a splitter used in the intermediate portion of a deployment network, where fiber optic strands are separated and directed to different locations. Distribution splitters divide a single fiber optic strand into multiple numbers of strands.
The number of splitters in a network depends on the total number of strands in the fiber optic cable leading into a central office. The total number of strands in the cable is at least equal to the number of fiber optic electronic devices connected at the central office.
For purposes of describing the present invention, it is understood that, although only two levels of splitting are described herein, any number of levels could be used to divide a primary fiber optic strand into multiple strands. In fact, instead of using distribution splitters and local terminals, a single primary fiber optic strand could go directly to a local terminal with a 1xc3x9732 splitter, in which case the local terminal splits the strand into 32 separate strands which may be connected to 32 individual fiber optic drops leading to one or more subscriber premises.
4. Secondary fiber optic strandxe2x80x94the strands that are separated from a primary fiber optic strand. When a primary fiber optic strand goes through a first distribution splitter, the separated strands are referred to as secondary fiber optic strands. The number of secondary fiber optic strands in the network depends upon the configuration of the splitter, e.g., a 1xc3x978 splitter would split a primary fiber optic strand into eight secondary fiber optic strands. Through each set of splitters, the number of fiber optic electronic devices supported becomes progressively smaller until there is only one device per strand.
5. Splice case or splicerxe2x80x94case that attaches to a fiber optic cable and separates one or more fiber optic strands from the cable to be diverted away from the cable in a different direction. A splice case contains fiber optic splices or permanent connections between two fiber optic strands.
6. Local terminalxe2x80x94an outside plant cable terminal used in the prior art for terminating one or more fiber optic strands near one or more subscriber premises for connection to copper wire drops into each subscriber premises. Under the current invention, a local terminal includes a splitter-terminal apparatus that splits a final fiber optic strand into multiple strands, each fitted with a connectorized termination for joining one fiber optic drop.
7. Fiber optic dropsxe2x80x94small fiber optic cables that contain one or two fiber optic strands connecting, for example, the local terminal to a fiber optic interface device or a fiber optic interface device to an optical network terminal.
8. Connectorized terminationxe2x80x94a fitting for a fiber optic cable or strand that facilitates quick connections between two different cables or strands. The fittings are typically plastic connectors with a male and female side, e.g., SC connectors.
9. Pigtailxe2x80x94in the context of a splitter-terminal, pigtail refers to a short length of jacketed fiber optic strand permanently fixed to a component at one end and a connectorized termination at the other end, such that the pigtail provides a flexible fiber optic connection between the component and the connectorized termination. When used in the context of a fiber optic drop, pigtail refers to a short length of jacket (the fiber optic strand is described separately) fixed to a component (sheath) at one end and a connectorized termination at the other end.
The telecommunications industry has long recognized the many advantages fiber optic cabling and transmission devices hold over traditional copper wire and transmission systems. Fiber optic systems provide significantly higher bandwidth and greater performance and reliability than standard copper wire systems. For example, fiber optic systems can transmit up to 10 gigabits per second (Gbps), while copper lines transmit at typically less than 64 kilobits per second (Kbps). Optical fibers also require fewer repeaters over a given distance to keep a signal from deteriorating. Optical fibers are immune to electromagnetic interference (from lightning, nearby electric motors, and similar sources) and to crosstalk from adjoining wires. Additionally, cables of optical fibers can be made smaller and lighter than conventional copper wire or coaxial tube cables, yet they can carry much more information, making them useful for transmitting large amounts of data between computers and for carrying bandwidth-intensive television pictures or many simultaneous telephone conversations.
Despite the many advantages, extremely high installation costs have discouraged network providers from providing continuous fiber optic networks extending from central office facilities all the way to subscriber premises. As used herein, xe2x80x9cfiber to the homexe2x80x9d (FTTH) refers to this continuous deployment of fiber optic lines directly to subscriber premises. On the main distribution lines of a telecommunications network, the volume of traffic and number of customers often justify the high installation cost of fiber optic lines. However, thus far, the costs of deploying fiber optic lines to individual subscriber premises have far outweighed any potential benefits to network providers.
Therefore, instead of implementing FTTH networks, service providers have developed strategies to provide some of the benefits of fiber optic networks without actually deploying fiber all the way to the home (or other end-subscriber location). One such strategy is known as fiber to the curb (FTTC), in which fiber optic lines extend from the service provider to local terminals (also referred to as outside plant cable terminals) that are situated in areas having a high concentration of subscribers. Service providers complete the last leg of the network, i.e., from the local terminals into a subscriber premises, using copper wire drops and perhaps a high speed data connection, such as an Asynchronous Digital Subscriber Line (ADSL).
Such FTTC systems provide the benefits of fiber optic systems as far as the fiber extends, but deprive the subscriber of the full benefit of fiber optic networks because of the copper wire drops. Indeed, as the weakest link, the copper wire drops limit the bandwidth capacity for the entire system. Thus, the only way to gain the full benefit of fiber optic networking is to use a continuous fiber optic connection from the service provider""s equipment to the subscriber""s equipment.
Despite the bandwidth limitations, network providers favor copper wire drops because of the prohibitively high cost of installing fiber optic drops using conventional systems and methods. The bulk of these costs can be attributed to the highly skilled labor and time required to install fiber optic splitters and to join fiber optic drops to fiber optic strands coming from the splitters. In conventional systems and methods, fiber optic networks use fiber optic splitters and splice cases to route fiber optic strands throughout a distribution network. The fiber optic splitters and splice cases allow a fiber optic strand to branch into multiple strands to widen a network""s coverage area. In conventional networks, design engineers use splitters and splice cases to route strands from electronic devices at the central office to distribution locations, such as those in housing developments.
To provide fiber optic drops to individual subscriber premises from the distribution locations, network providers could manually splice individual fiber optic drops onto each strand. Or, alternatively, each time that a new subscriber requires fiber optic service, a network provider could manually fit the fiber optic strands with a connector for joining a fiber optic drop that runs to the new subscriber""s premises. However, whether manually splicing individual fiber optic drops or fitting fiber optic strands with connectors for each service request, network providers must use highly skilled technicians to complete the specialized tasks. These technicians tend to be both expensive and in short supply. Thus, in light of the conventional systems and methods for deploying fiber optic cable, network providers rightly view the deployment of individual fiber optic drops from these distribution locations as an expensive and time-consuming endeavor.
To avoid the high costs of manually splicing fiber or fitting connectors onto fiber, network providers could use conventional fiber optic splitters to facilitate connections. However, conventional fiber optic splitter apparatus are difficult to connect. The fiber optic splitters known in the prior art are designed to accommodate permanent connections. The splitters are installed at network branch locations at which the number and structure of incoming and outgoing strands rarely change. In contrast, in deploying fiber to the home from the distribution locations, network providers must have the flexibility to add and disconnect services on an individual subscriber level. Thus, the permanent nature of conventional fiber optic splitter apparatus is inappropriate for fiber to the home deployment.
Thus, in a typical network, instead of providing fiber optic drops from the distribution locations to the subscriber premises, network providers run fiber optic strands from the distribution locations to electronic devices located in local terminals, e.g., aerial or buried terminals. These local terminals are situated in the center of a cluster of subscriber houses. The fiber optic service ends at these local terminals, and copper wire drops complete the connection to the subscriber premises. The copper wire drops are used because no device exists in the prior art that facilitates an economical, easy-to-connect fiber optic drop to the subscriber premises. Although the prior art includes fiber optic splitters and splices for network deployment, the existing splitters and splices are not appropriate for installing individual drops to subscribers because they do not provide a terminating function and they are not combined into an easy-to-deploy unit.
In addition, because the prior art lacks a device to connect a fiber optic drop to a subscriber premises, the prior art also lacks devices for implementing fiber to the home from the distribution locations to the subscriber""s equipment inside the subscriber""s premises. Thus far, connecting distribution locations to subscriber equipment has been limited to copper. Devices that bring copper from the curb into the home are well known in the art. For example, one such device is a network interface device produced by Corning Cable Systems of Hickory, N.C. In stark contrast, however, the prior art lacks devices dedicated to bringing fiber from the curb to the home.
The present invention is a connectorized outside fiber optic drop that facilitates the deployment of fiber to the home. The connectorized outside fiber drop includes a sheath, transition fittings, pigtails, fiber optic connectors, and a fiber optic strand. The sheath is positioned over a middle section of the fiber optic strand. The transition fittings are attached to the sheath proximate to both ends of the outside fiber optic drop. The pigtails attach to the transition fittings and enclose the fiber optic strand from the transition fittings to the ends of the fiber optic strand, where the fiber optic connectors are attached to the fiber optic strand and the pigtails. If the drop contains more than one fiber optic strand, then one set of pigtails with connectors is provided for each fiber optic strand.
In facilitating the deployment of fiber to the home, the present invention functions within a fiber optic network that provides continuous fiber optic strands from a service provider""s central office to individual subscriber""s premises. As shown schematically in FIG. 1a, the network comprises a central office fiber optic electronic device, a primary fiber optic cable (or strand), distribution splitters, secondary fiber optic cables (or strands), local terminals (outside plant cable terminals), and fiber optic drops to subscriber premises. In replacing the inferior fiber to the curb deployments of the prior art, the present invention facilitates a system that economically deploys complete, uninterrupted fiber optic services to individual subscribers.
To facilitate fiber to the home, the present invention helps connect the local terminals of the network to the subscriber premises, i.e., the present invention helps to extend fiber from the xe2x80x9ccurbxe2x80x9d to the xe2x80x9chome.xe2x80x9d As shown in FIG. 1b, this portion of the network includes a fiber optic splitter-terminal apparatus in the local terminal, the connectorized outside fiber drop of the present invention in communication with the fiber optic splitter-terminal apparatus, a fiber optic interface device in communication with the connectorized outside fiber drop, and a connectorized inside fiber drop in communication with the fiber optic interface device. The connectorized inside fiber drop connects to optical network terminals in the subscriber premises, which in turn connect to the subscriber""s fiber optic electronic devices. The fiber optic electronic devices connect to home consumer electronic devices, such as personal computers or telephones. Together, these components enable the cost-effective installation of fiber to the home.
Accordingly, an object of the present invention is to provide a fiber optic network that delivers uninterrupted fiber optic service from a central office to subscriber premises.
Another object of the present invention is to provide an inexpensive apparatus that connects a local terminal to a fiber optic interface device.
Another object of the present invention is to provide an outside fiber optic drop that can be installed without requiring splicing.